An attempt to refine rockfall hazard zoning based on the kinetic energy, frequency and fragmentation degree

Abstract

Abstract. Rockfall hazard zoning is usually achieved using a qualitative estimate of hazard, and not an absolute scale. In Switzerland, danger maps, which correspond to a hazard zoning depending on the intensity of the considered phenomenon (e.g. kinetic energy for rockfalls), are replacing hazard maps. Basically, the danger grows with the mean frequency and with the intensity of the rockfall. This principle based on intensity thresholds may also be applied to other intensity threshold values than those used in Switzerland for rockfall hazard zoning method, i.e. danger mapping.In this paper, we explore the effect of slope geometry and rockfall frequency on the rockfall hazard zoning. First, the transition from 2D zoning to 3D zoning based on rockfall trajectory simulation is examined; then, its dependency on slope geometry is emphasized. The spatial extent of hazard zones is examined, showing that limits may vary widely depending on the rockfall frequency. This approach is especially dedicated to highly populated regions, because the hazard zoning has to be very fine in order to delineate the greatest possible territory containing acceptable risks.

Integrating rockfall risk assessment and countermeasure design by 3D modelling techniques

“…Thus, rockfall protection through both structural and landplanning actions is an important issue for administrators and stakeholders in rockfall prone areas (Raetzo et al, 2002; Correspondence to: F. Agliardi (federico.agliardi@unimib.it) and Corominas et al, 2005;Jaboyedoff et al, 2005;Straub and Schubert, 2008;Fell et al, 2008). Rockfall protection includes different tasks, namely: rockfall risk assessment for land planning and prioritization of actions; identification of mitigation options able to achieve a specified risk reduction; and evaluation of their cost efficiency to optimise budget and design.…”

“…Thus, a Quantitative Risk Analysis (QRA; Corominas et al, 2005;Fell et al, 2005) for these processes should be based on sound modelling of rockfall processes. Nevertheless, few researchers applied risk analysis to the design and evaluation of rockfall protection measures (Bunce et al, 1997;Hungr et al, 1999;Corominas et al, 2005;Straub and Schubert,1060 F. Agliardi et al: Integrating rockfall risk assessment and countermeasure design We integrated all the relevant stages of the rockfall protection process in a comprehensive approach which takes advantage of 3D mathematical modelling, providing useful insight and tools for the analysis of rockfall processes and related risks Crosta and Agliardi, 2003;Jaboyedoff et al, 2005;Frattini et al, 2008). We present the case study of Fiumelatte (Lecco, Italy; Fig.…”

Quantitative assessment of diffuse rock fall hazard along a cliff foot

“…(6) and (13) gives the hazard only if the element at risk is close enough to the rock wall so that the probability of propagation equals 1. Otherwise the probability of propagation must be taken into account (see for example Guzzetti et al, 2002;Jaboyedoff et al, 2005). …”

“…Without such an inventory, a qualitative assessment is achieved, mainly based on expert judgment (Groupe Falaise, 2001;Hantz et al, 2003b;Effendiantz et al, 2004). Examples of quantitative rock fall hazard and risk assessment are given by Hungr et al (1999, Picarelli et al (2005), Corominas et al (2005), Jaboyedoff et al (2005), Agliardi et al (2009), andAbbruzzese et al (2009). In these examples, a given volume range of rock falls is considered.…”

Identification of potential rockfall source areas at a regional scale using a DEM-based geomorphometric analysis

“…Besides, high resolution DEMs (HRDEMs) have made possible the detection A. Loye et al: Potential rockfall source areas using a DEM-based geomorphometric analysis of discontinuities sets (Jaboyedoff et al, 2007). Considering the spatial arrangement of discontinuities with the topography, a kinematic analysis can then be performed to detect potential failure mechanisms (planar sliding, wedge failure and toppling) (Wagner et al, 1988;Rouiller et al, 1998;Gokceoglu et al, 2000;Jaboyedoff et al, 2004bJaboyedoff et al, , 2005bGünther et al, 2004;Derron et al, 2005). Those geometrical and geomechanical-based approaches are especially suitable for slope stability analyses in well-known regions where rockfall cause problems.…”